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Octafluorocyclobutane
Octafluorocyclobutane, or perfluorocyclobutane, C4F8, is an organofluorine compound which enjoys several niche applications. Octafluorocyclobutane is a colourless gas and shipped as a liquefied gas. It is the perfluorinated analogue of cyclobutane whereby all C–H bonds are replaced with C–F bonds. Production Octafluorocyclobutane is produced by the dimerization of tetrafluoroethylene and the reductive coupling of 1,2-dichloro-1,1,2,2-tetrafluoroethane.. Applications In the production of semiconductor materials and devices, octafluorocyclobutane serves as a deposition gas and etchant.{{cite web , url = http://encyclopedia.airliquide.com/Encyclopedia.asp?GasID=50#GeneralData , work = Gas Encyclopaedia , publisher = Air Liquide , title = Octafluorocyclobutane (RC318) , accessdate = May 15, 2013 It has also been investigated as a refrigerant in specialised applications, as a replacement for ozone depleting chlorofluorocarbon refrigerants. Exploiting its volatility and che ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dielectric Gas
A dielectric gas, or insulating gas, is a dielectric material in gaseous state. Its main purpose is to prevent or rapidly quench electric discharges. Dielectric gases are used as electrical insulators in high voltage applications, e.g. transformers, circuit breakers (namely sulfur hexafluoride circuit breakers), switchgear (namely high voltage switchgear), radar waveguides, etc. A good dielectric gas should have high dielectric strength, high thermal stability and chemical inertness against the construction materials used, non-flammability and low toxicity, low boiling point, good heat transfer properties, and low cost. The most common dielectric gas is air, due to its ubiquity and low cost. Another commonly used gas is a dry nitrogen. In special cases, e.g., high voltage switches, gases with good dielectric properties and very high breakdown voltages are needed. Highly electronegative elements, e.g., halogens, are favored as they rapidly recombine with the ions present in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclobutane
Cyclobutane is a cycloalkane and organic compound with the formula (CH2)4. Cyclobutane is a colourless gas and commercially available as a liquefied gas. Derivatives of cyclobutane are called cyclobutanes. Cyclobutane itself is of no commercial or biological significance, but more complex derivatives are important in biology and biotechnology. Structure The bond angles between carbon atoms are significantly strained and as such have lower bond energies than related linear or unstrained hydrocarbons, e.g. butane or cyclohexane. As such, cyclobutane is unstable above about 500 °C. The four carbon atoms in cyclobutane are not coplanar; instead the ring typically adopts a folded or "puckered" conformation. This implies that the C-C-C angle is less than 90°. One of the carbon atoms makes a 25° angle with the plane formed by the other three carbons. In this way some of the eclipsing interactions are reduced. The conformation is also known as a "butterfly". Equivalent p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organofluorine Chemistry
Organofluorine chemistry describes the chemistry of the organofluorines, organic compounds that contain the carbon–fluorine bond. Organofluorine compounds find diverse applications ranging from Lipophobicity, oil and hydrophobe, water repellents to pharmaceuticals, refrigerants, and reagents in catalysis. In addition to these applications, some organofluorine compounds are pollutants because of their contributions to ozone depletion, global warming, bioaccumulation, and toxicity. The area of organofluorine chemistry often requires special techniques associated with the handling of fluorinating agents. The carbon–fluorine bond Fluorine has several distinctive differences from all other substituents encountered in organic molecules. As a result, the physical and chemical properties of organofluorines can be distinctive in comparison to other organohalogens. # The carbon–fluorine bond is one of the strongest in organic chemistry (an average bond energy around 480 kJ/molKirsch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Refrigerants
A refrigerant is a working fluid used in the refrigeration cycle of air conditioning systems and heat pumps where in most cases they undergo a repeated phase transition from a liquid to a gas and back again. Refrigerants are heavily regulated due to their toxicity, flammability and the contribution of CFC and HCFC refrigerants to ozone depletion and that of HFC refrigerants to climate change. Refrigerants are used in a Direct Expansion (DX) system to transfer energy from one environment to another, typically from inside a building to outside (or vice versa) commonly known as an "air conditioner" or "heat pump". Refrigerants can carry per kg 10 times more energy than water and 50 times more than air. Refrigerants are controlled substances due to 1) High Pressures (100-145 psi), 2) Extreme temperatures (-50°C to 145°C), 3) Flammability A1 class non-flammable, A2/A2L class flammable & A3 class extremely flammable/explosive and 4) Toxicity B1-low, B2-medium & B3-high, as classifie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aerosol Propellants
Aerosol spray is a type of dispensing system which creates an aerosol mist of liquid particles. It comprises a can or bottle that contains a payload, and a propellant under pressure. When the container's valve is opened, the payload is forced out of a small opening and emerges as an aerosol or mist. History The concepts of aerosol probably go as far back as 1790.Bellis, MarThe History of Aerosol Spray Cans/ref> The first aerosol spray can patent was granted in Oslo in 1927 to Erik Rotheim, a Norwegian chemical engineer,Norwegian Patent No. 46613, issued on November 23, 1926 and a United States patent was granted for the invention in 1931. — Method and Means for the Atomizing or Distribution of Liquid or Semiliquid Materials, issued April 7, 1931 The patent rights were sold to a United States company for 100,000 Norwegian kroner. The Norwegian Postal Service, Posten Norge, celebrated the invention by issuing a stamp in 1998. In 1939, American Julian S. Kahn received a pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Critical Point (thermodynamics)
In thermodynamics, a critical point (or critical state) is the end point of a phase equilibrium curve. The most prominent example is the liquid–vapor critical point, the end point of the pressure–temperature curve that designates conditions under which a liquid and its vapor can coexist. At higher temperatures, the gas cannot be liquefied by pressure alone. At the critical point, defined by a ''critical temperature'' ''T''c and a ''critical pressure'' ''p''c, phase boundaries vanish. Other examples include the liquid–liquid critical points in mixtures, and the ferromagnet–paramagnet transition (Curie temperature) in the absence of an external magnetic field. Liquid–vapor critical point Overview For simplicity and clarity, the generic notion of ''critical point'' is best introduced by discussing a specific example, the vapor–liquid critical point. This was the first critical point to be discovered, and it is still the best known and most studied one. The figu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfur Hexafluoride
Sulfur hexafluoride or sulphur hexafluoride (British spelling) is an inorganic compound with the formula SF6. It is a colorless, odorless, non- flammable, and non-toxic gas. has an octahedral geometry, consisting of six fluorine atoms attached to a central sulfur atom. It is a hypervalent molecule. Typical for a nonpolar gas, is poorly soluble in water but quite soluble in nonpolar organic solvents. It has a density of 6.12 g/L at sea level conditions, considerably higher than the density of air (1.225 g/L). It is generally transported as a liquefied compressed gas. is 23,500 times more potent than as a greenhouse gas but exists in relatively minor concentrations in the atmosphere. Its concentration in Earth's troposphere reached 10.63 parts per trillion (ppt) in 2021, rising at 0.39 ppt/year. The increase over the prior 40 years was driven in large part by the expanding electric power sector, including fugitive emissions from banks of gas contained in its med ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Codex Alimentarius
The Codex Alimentarius () is a collection of internationally recognized standards, codes of practice, guidelines, and other recommendations published by the Food and Agriculture Organization of the United Nations relating to food, food production, food labeling, and food safety. History and governance Its name is derived from the Codex Alimentarius Austriacus. Its texts are developed and maintained by the Codex Alimentarius Commission (CAC), a body established in early November 1961 by the Food and Agriculture Organization of the United Nations (FAO), was joined by the World Health Organization (WHO) in June 1962, and held its first session in Rome in October 1963. The Commission's main goals are to protect the health of consumers, to facilitate international trade, and ensure fair practices in the international food trade.Understanding Codex', World Health Organization and the Food and Agriculture Organization of the United Nations (5th ed. Sept. 2018). The CAC is an intergov ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chlorofluorocarbon
Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and propane. They are also commonly known by the DuPont brand name Freon. The most common representative is dichlorodifluoromethane (R-12 or Freon-12). Many CFCs have been widely used as refrigerants, propellants (in aerosol applications), and solvents. Because CFCs contribute to ozone depletion in the upper atmosphere, the manufacture of such compounds has been phased out under the Montreal Protocol, and they are being replaced with other products such as hydrofluorocarbons (HFCs) including R-410A and R-134a. Structure, properties and production As in simpler alkanes, carbon in the CFCs bond with tetrahedral symmetry. Because the fluorine and chlorine atoms differ greatly in size and effective charge from hydrogen and from each other, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ozone Depleting
Ozone depletion consists of two related events observed since the late 1970s: a steady lowering of about four percent in the total amount of ozone in Earth's atmosphere, and a much larger springtime decrease in stratospheric ozone (the ozone layer) around Earth's polar regions. The latter phenomenon is referred to as the ozone hole. There are also springtime polar tropospheric ozone depletion events in addition to these stratospheric events. The main causes of ozone depletion and the ozone hole are manufactured chemicals, especially manufactured halocarbon refrigerants, solvents, propellants, and foam-blowing agents (chlorofluorocarbons (CFCs), HCFCs, halons), referred to as ozone-depleting substances (ODS). These compounds are transported into the stratosphere by turbulent mixing after being emitted from the surface, mixing much faster than the molecules can settle. Once in the stratosphere, they release atoms from the halogen group through photodissociation, which catalyze t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Refrigerant
A refrigerant is a working fluid used in the heat pump and refrigeration cycle, refrigeration cycle of air conditioning systems and heat pumps where in most cases they undergo a repeated phase transition from a liquid to a gas and back again. Refrigerants are heavily regulated due to their toxicity, flammability and the contribution of CFC and HCFC refrigerants to ozone depletion and that of HFC refrigerants to climate change. Refrigerants are used in a Direct Expansion (DX) system to transfer energy from one environment to another, typically from inside a building to outside (or vice versa) commonly known as an "air conditioner" or "heat pump". Refrigerants can carry per kg 10 times more energy than water and 50 times more than air. Refrigerants are controlled substances due to 1) High Pressures (100-145 psi), 2) Extreme temperatures (-50°C to 145°C), 3) Flammability A1 class non-flammable, A2/A2L class flammable & A3 class extremely flammable/explosive and 4) Toxicity B1-low ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
